This invention relates in general to microwave directional antennas and in particular to a new and useful microwave directional antenna particularly for the millimeter-wave range.
In the design of directional antennas strongly focusing in two planes, three antenna systems are usually employed in the microwave and millimeter-wave ranges: (1) Horn radiators, (2) Antenna arrays, (3) reflector antennas.
Horn radiators are used in practice only for antennas having a directive gain less than 25 db, since at higher gains a too long horn radiator and thus an unhandy antenna structure would be obtained. Antenna arrays, such as waveguide slot antennas, save much space (they are planar), however, their design and manufacture are expensive. Antenna arrays in the form of etched halfwave resonators in microstrip technique are also very flat, their gains are not too high, however, because of the inevitable losses. Reflector antennas, such as parabolic mirror antennas, are simple to construct and transmit a very broad band, only they are not flat enough for many applications.